This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2001-095027, filed Mar. 29, 2001, No. 2001-095029, field Mar. 29, 2001; and No. 2001-198088, filed Jun. 29, 2001, the entire contents of all of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a negative electrode active material and a nonaqueous electrolyte battery.
2. Description of the Related Art
Nowadays, a lithium secondary battery has been commercialized as a nonaqueous electrolyte secondary battery for a portable equipment such as a portable telephone. The lithium secondary battery comprises a positive electrode containing a lithium cobalt oxide such as LiCoO2 as a positive electrode active material, a negative electrode containing a carbonaceous material as a negative electrode active material, and a nonaqueous electrolyte prepared by dissolving a lithium salt in an organic solvent.
In recent years, the power consumption of a portable equipment is being increased in accordance with increase in the number of required functions and with elevation in the required performance of the equipment. In this connection, demands for a larger capacity are being made stronger in respect of the battery providing the power source of the portable equipment. Under the circumstances, efforts to develop new electrode materials that are expected to increase the battery capacity are being made vigorously.
Known metal sulfides used as the negative electrode active material in a nonaqueous electrolyte battery include, for example, FeS2, CuS and NiS. Particularly, FeS2, which performs a four-electron reaction and has such a high theoretical capacity as about 894 mAh/g, is a hopeful metal sulfide.
However, the Fe-containing sulfide such as FeS2 is low in reversibility of the reaction taking place in the charge-discharge time. As a result, the secondary battery comprising an Fe-containing sulfide as a negative electrode active material gives rise to the problem that the cycle life is short. Particularly, the decrease of the cycle life was serious in the case of using a liquid material as the nonaqueous electrolyte.
An object of the present invention is to provide a nonaqueous electrolyte battery exhibiting an improved cycle life, and to provide a negative electrode active material capable of exhibiting an improved cycle life.
Another object of the present invention is to provide a nonaqueous electrolyte battery exhibiting an improved energy density, and to provide a negative electrode active material capable of exhibiting an improved energy density.
According to a first aspect of the present invention, there is provided a nonaqueous electrolyte battery, comprising:
a positive electrode containing a positive electrode active material;
a negative electrode containing a sulfide containing Fe; and
a nonaqueous electrolyte including a nonaqueous solvent and a solute dissolved in the nonaqueous solvent, the nonaqueous solvent containing a first solvent containing a cyclic carbonate and a second solvent containing a chain carbonate;
wherein the content of the first solvent in the nonaqueous solvent falls within a range of between 4.8 and 29% by volume and the content of the second solvent in the nonaqueous solvent falls within a range of between 71 and 95.2% by volume.
According to a second aspect of the present invention, there is provided a nonaqueous electrolyte battery, comprising:
a positive electrode containing a positive electrode active material;
a negative electrode containing a sulfide containing Fe; and
a nonaqueous electrolyte including a nonaqueous solvent, the nonaqueous solvent comprising a first solvent containing a cyclic carbonate and a second solvent containing a chain carbonate, and a solute dissolved in the nonaqueous solvent, the mixing ratio of the first solvent and the second solvent satisfying formula (1):
S1:S2=1:2.5 to 1:20xe2x80x83xe2x80x83(1) 
where S1 represents the volume ratio of the first solvent, and S2 represents the volume ratio of the second solvent.
According to a third aspect of the present invention, there is provided a negative electrode active material capable of absorbing-desorbing an alkali metal, the negative electrode active material containing a compound having a composition represented by formula (4):
AzFe(1xe2x88x92x)MxSyxe2x80x83xe2x80x83(4) 
where xe2x80x9cAxe2x80x9d contains at least one kind of an alkali metal, xe2x80x9cMxe2x80x9d contains at least one element selected from the group consisting of Cu, Ni, Co, Mn, Mg, Al, Si and Cr, the molar ratio x falls within a range of between 0.0003 and 0.03, i.e., 0.0003xe2x89xa6xxe2x89xa60.03, the molar ratio y falls within a range of between 1.08 and 1.33, i.e., 1.08xe2x89xa6yxe2x89xa61.33, and the molar ratio z is not higher than 2, i.e., 0xe2x89xa6zxe2x89xa62.
According to a fourth aspect of the present invention, there is provided a nonaqueous electrolyte battery, comprising:
a positive electrode;
a negative electrode containing a negative electrode active material capable of absorbing-desorbing an alkali metal; and
a nonaqueous electrolyte;
wherein the negative electrode active material contains a compound having a composition represented by formula (4):
AzFe(1xe2x88x92x)MxSyxe2x80x83xe2x80x83(4) 
where xe2x80x9cAxe2x80x9d contains at least one kind of an alkali metal, xe2x80x9cMxe2x80x9d contains at least one element selected from the group consisting of Cu, Ni, Co, Mn, Mg, Al, Si and Cr, the molar ratio x falls within a range of between 0.0003 and 0.03, i.e., 0.0003xe2x89xa6xxe2x89xa60.03, the molar ratio y falls within a range of between 1.08 and 1.33, i.e., 1.08xe2x89xa6yxe2x89xa61.33, and the molar ratio z is not higher than 2, i.e., 0xe2x89xa6zxe2x89xa62.
According to a fifth aspect of the present invention, there is provided a negative electrode active material capable of absorbing-desorbing an alkali metal, the negative electrode active material containing a sulfide containing P and at least one kind of a metal element selected from the group consisting of Fe, Ni, Co, Mn and Cu.
According to a sixth aspect of the present invention, there is provided a negative electrode active material capable of absorbing-desorbing an alkali metal, the negative electrode active material containing a compound having a composition represented by formula (5):
AaM1PbScxe2x80x83xe2x80x83(5) 
where xe2x80x9cAxe2x80x9d includes at least one kind of an alkali metal element, xe2x80x9cM1xe2x80x9d includes at least one kind of an element selected from the group consisting of Fe, Ni, Co, Mn and Cu, the molar ratio xe2x80x9call falls within a range of between 0 and 12, i.e., 0xe2x89xa6axe2x89xa612, the molar ratio xe2x80x9cbxe2x80x9d falls within a range of between 0.1 and 1.1, i.e., 0.1xe2x89xa6bxe2x89xa61.1, and the molar ratio xe2x80x9ccxe2x80x9d falls within a range of between 0.9 and 3.3, i.e., 0.9xe2x89xa6cxe2x89xa63.3.
According to a seventh aspect of the present invention, there is provided a nonaqueous electrolyte battery, comprising:
a positive electrode;
a negative electrode containing a negative electrode active material capable of absorbing-desorbing an alkali metal; and
a nonaqueous electrolyte;
wherein the negative electrode active material contains a sulfide containing P and at least one metal element selected from the group consisting of Fe, Ni, Co, Mn and Cu.
According to an eighth aspect of the present invention, there is provided a nonaqueous electrolyte battery, comprising:
a positive electrode;
a negative electrode containing a negative electrode active material capable of absorbing-desorbing an alkali metal; and
a nonaqueous electrolyte;
wherein the negative electrode active material contains a compound having a composition represented by formula (5):
AaM1PbScxe2x80x83xe2x80x83(5) 
where xe2x80x9cAxe2x80x9d includes at least one kind of an alkali metal element, xe2x80x9cM1xe2x80x9d includes at least one kind of an element selected from the group consisting of Fe, Ni, Co, Mn and Cu, the molar ratio xe2x80x9caxe2x80x9d falls within a range of between 0 and 12, i.e., 0xe2x89xa6axe2x89xa612, the molar ratio xe2x80x9cbxe2x80x9d falls within a range of between 0.1 and 1.1, i.e., 0.1xe2x89xa6bxe2x89xa61.1, and the molar ratio xe2x80x9ccxe2x80x9d falls within a range of between 0.9 and 3.3, i.e., 0.9xe2x89xa6cxe2x89xa63.3.